1. Field of the Invention
The invention pertains to the method and apparatus of printing the side edges of stacked sheets, such as the pages of a catalog, with type to produce a dense sharp image on the sheet edges.
2. Description of the Related Art
In the manufacture and assembly of stacked sheets, particularly those sheets constituting a book, catalog, reference materials, specification sheets, or the like, it is often desirable that indicia and information appear on the side edges of the stack of sheets. Such indicia may be for the purpose of indicating the location of the contents of the stacked sheets, or may constitute advertising or other information.
In the past, considerable difficulty has been encountered in the application of indicia to the edges of stacked sheets. Such difficulty is a combination of several factors, such as the fact that the stacked sheets constitute a plurality of substrata each only exposing a very thin edge to the ink or marking material. It has been difficult, during the printing of the edges of stacked material, to maintain the stacked sheets in a properly aligned and oriented manner, and in the past most indicia applied to the side edges of books, catalogs, reference material, and the like, have been applied by a digital sprayed jet process wherein the image is produced by a plurality of small jet sprayed dots. The use of a jet to form side edge printing does not result in a dense and sharp image, and as the stacked material is "fanned" the image is further blurred and dissipated. The need for an improved side edge printer for stacked sheets has long been recognized.